Abstract -

The study presents the depth and areal distribution of Cs-137 activity concentration in the forest soils of Farkas Trench, a small water catchment in the Sopron Mountains, in 2001 and 2010, moreover the possible reason of the alteration in activity concentration. The Cs-137 activity values were measured in 30 plots in 2001, and in 5 in 2010. In 2001, the depth distribution of Cs-137 activity concentration in the measurement plots was shaped in accordance with a decreasing exponential function. It appeared in the 2010 data that the highest Cs-137 activity concentration had shifted lower from the top layers, and the depth distribution changed along an increasing or a stagnating function until a depth of 4 to 6 cm (in function of slope inclination), then along a decreasing function. In 2001, activity concentration in the surface soil layers (0 - 2 cm) altered between 15 and 609 Bq/kg, whereas in 2010 between 26 and 72 Bq/kg. A correlation was found between activity concentration in the surface soil layer and slope inclination. It was concluded that one of the main reasons for differences in distribution of Cs-137 activity concentration was the differing extent of soil movement.